The invention generally relates to electro-optics, and more specifically relates to analysis and control of timing of trains of high speed optical pulses.
Initially, trains of high speed, high power laser pulses could only be generated by specially trained technicians utilizing a room full of complex and specialized laboratory equipment. Especially challenging is precise control of timing attributes, such as temporal placement and duration of each pulse of the train.
It may be possible to monitor temporal placement and duration of each pulse of such trains of high speed, high power laser pulses using previously known arrangements, such as extremely high speed sample and hold circuits. Additionally, it may be possible to precisely control such timing attributes of optical pulses using microwave frequency clock signals. While these arrangements provide some advantages, they are typically relatively complex, expensive, and difficult to manufacture, use and maintain.
Today, because of mass production and mass merchandising of consumer electronic devices such as readable/re-writeable Compact Disc (CD) drives, Digital Versatile Disc (DVD) drives and the like, ordinary people can generate a train of high speed, high power laser pulses within an area less then five and one quarter inches wide (of course, most such people are unaware that they are doing so.)
Write operations typically require that write pulses within the pulse train last for only approximately sixteen to approximately eight nanoseconds or less. It is desirable to vary temporal placement and duration of pulses in accordance a so called xe2x80x9cWRITE STRATEGYxe2x80x9d, which is based in part on physical properties, for example thermodynamic properties, of a layer of disc media that interacts with the laser pulse train.
Examples of various respective xe2x80x9cWRITE STRATEGIESxe2x80x9d are specified in the European Computer Manufacturers Association (ECMA) Standard ECMA-279 80 mm (1,23 Gbytes per side) and 120 mm (3,95 Gbytes per side) DVD-Recordable Disk (DVD-R), December 1998: BASIC WRITE STRATEGY page 21 section 4.3; and VARIATION OF THE WRITE STRATEGY page 103 Annex P.
Many vendors of consumer electronic devices implement a WRITE STRATEGY by varying temporal placement and duration of optical pulses using a primarily digital method, which is limited by relatively small integral numbers of relatively low frequency clock pulses. For example: a five hundred megahertz (500 Mhz) frequency electronic clock is employed; flexibility and precision of temporal placement is limited to integral multiples of two nanoseconds (one clock cycle); six consecutive electrical pulses of the clock are used to provide a twelve nanosecond duration optical pulse; four consecutive electrical pulses of the clock are used to provide an eight nanosecond duration optical pulse; and seven consecutive electrical pulses of the clock are used to provide a fourteen nanosecond duration optical pulse. Accordingly, in this example flexibility and precision of the implementation of the WRITE STRATEGY is limited to optical pulses having durations of twelve, eight, or fourteen nanoseconds.
Of course, precision of implementations of the WRITE STRATEGY using the primarily digital method could be improved by using relatively larger number of relatively higher, microwave frequency clock pulses. However, this would add undesired complexity expense, and difficulty in manufacturing, use and maintenance of consumer electronic devices.
What is needed for consumer electronic devices is a relatively simple (and relatively easy to manufacture, use and maintain) apparatus and method for flexibly and precisely varying temporal placement and duration of pulses, within a train of high speed, high power optical pulses.
The invention provides a relatively simple (and relatively easy to manufacture, use and maintain) apparatus and method for flexibly and precisely varying temporal placement and duration of pulses, within a train of high speed, high power optical pulses. These aspects of the invention make it particularly advantageous for use in consumer electronics devices such as readable/re-writeable Compact Disc (CD) drives, Digital Versatile Disc (DVD) drives and the like.
Briefly and in general terms the invention includes optics adapted for focusing on a layer of an information storage media. An optical pulse generator is coupled with the layer through the optics for generating a train of optical pulses, wherein each pulse has a respective temporal placement within the train and has a respective pulse duration. The respective pulse duration of each pulse is controlled by an amount of an analog duration control voltage, in accordance with a WRITE STRATEGY, which is based on a physical property of the layer of the information storage media. Similarly the respective temporal placement of each pulse is controlled by an amount of an analog temporal placement control voltage, in accordance with the WRITE STRATEGY.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.